This project seeks to determine whether the regulation of lens fiber differentiation and maturation is associated with alterations in the plasma membrane. To this end, the principal lipid and protein components of embryonic and adult chicken lens membranes are being identified, and their metabolism is being investigated. Because of the known involvement of phosphatidylinositol (PI) turnover and phosphatidylethanolamine (PE) methylation in regulatory mechanisms of various other cell types, the initial stages of this study have focused on lens phospholipid metabolism. Computer modeling of the kinetics of 32P incorporation into lens phospholipids in vivo is employed to determine the rates of synthesis and degradation of individual phospholipids. This approach is also being applied to the study of phospholipid metabolism in differentiating explants of embryonic ckick lens epithelia in organ culture, thus allowing the possible relationships between phospholipid metabolism and differentiation to be studied under controlled conditions.